JPH0214446B2 - - Google Patents

Description

[Detailed description of the invention]

In the continuous production of acrylonitrile-based carbon fibers, the present invention involves attaching a specific amount of a specific chemical substance to a flame-resistant fiber bundle to improve cohesiveness, prevent fuzzing that occurs in the fiber bundle, and defibrate agglutination. The present invention relates to a method for producing high-performance carbon fibers while preventing surface damage. More specifically, the present invention reduces the fluff and fiber waste that accumulates in the carbonization furnace, prevents narrowing of the yarn path, suppresses the generation of fluff on the fiber bundles passing through, and improves the guide to the furnace. It prevents fluffing and wrapping on rollers, and also defibrates agglutination caused during the flame-retardant process, and prevents surface damage to flame-retardant fibers and carbon fibers caused when passing through roller guides, resulting in high-performance carbon fibers. This is a method for producing fibers. Generally, to produce carbon fibers, acrylonitrile fiber bundles are made flame resistant in an oxidizing atmosphere at about 260°C to produce flame resistant fibers, and then in an inert atmosphere at about 260°C.
Carbonize at 1300℃ to make carbon fiber. A number of technical problems arise when such manufacturing methods are operated continuously. In other words, fluff and fiber waste accumulate in the furnace during carbonization, and the yarn path in the furnace is narrowed by the deposits, which causes fluff in the passing fiber bundles, and also causes the fiber bundles to become fluffy. Even when applied, the fiber bundles become fluffy. In the flame-retardant process of obtaining flame-resistant fibers from acrylonitrile fibers, a certain amount of adhesion between fibers is unavoidable, but if the degree of adhesion is large and it is not defibrated, the strength of the carbon fiber obtained by carbonization will decrease, resulting in high performance. carbon fiber cannot be obtained. 2 when flame-resistant fiber is carbonized in a furnace
When making carbon fiber by heat treatment in a stage carbonization furnace,
The fiber has to pass through a large number of rollers and presser roller guides, and at this time some degree of surface damage is usually inevitable, but the more surface damage there is, the more the strength of the carbon fiber decreases, and the high performance carbon fiber is I can't get it. The present invention solves all of these problems in the production of carbon fibers and obtains high-quality, high-performance carbon fibers. That is, the present invention is as follows. When the flame-resistant fiber bundle is supplied to a carbonization furnace and continuously heat-treated to produce acrylonitrile-based carbon fiber, the flame-resistant fiber bundle is preliminarily treated with polyethylene oxide having a molecular weight of 100,000 or more, ethyl ether, or hydroxyethyl ether. An aqueous solution of cellulose or (and) polyvinyl methyl ether is deposited, with an amount of deposited at 0.01 to 0.5% by weight, and then dried at a temperature of 250°C or less, followed by the heat treatment described above. A method for manufacturing carbon fiber. According to the present invention, deposits in a carbonization furnace can be significantly reduced, and fluff of the obtained carbon fibers can be significantly reduced. Further, by defibrating the flame-resistant fibers that have stuck together in the flame-retardant process, high-strength carbon fibers with less stickiness can be obtained, and furthermore, high-strength carbon fibers can be obtained by preventing surface damage. In the present invention, the flame-resistant fiber bundle of the fiber bundle to be treated is obtained from an acrylonitrile-based fiber bundle. Acrylonitrile fiber is a polymer or copolymer containing at least 90% by weight of an acrylonitrile component in its polymer component, and 0 to 10% by weight of acrylonitrile and a vinyl compound for copolymerization as a copolymer component. It is a fiber. As a fiber bundle, filament with a single fiber fineness of 0.5 to 1.5 denier is used.
A configuration with 100 to 30,000 pieces is usually used. The chemical substance (hereinafter referred to as "sizing agent") attached to the flame-resistant fiber bundle, which is the fiber bundle to be treated, is polyethylene oxide (PEO) with a molecular weight of 100,000 or more.
Preferably, PEO has a molecular weight of 100,000 to 4.8 million, particularly preferably 100,000 to 1.1 million. When the molecular weight is less than 100,000, the viscosity is low and the anti-fuzz effect cannot be obtained sufficiently. In the case of PEO, when the molecular weight exceeds 1.1 million, the viscosity tends to increase even at low concentrations. In this case, acetone, methanol, ethanol, etc. can also be added. Other sizing agents include ethyl etherified or hydroxyethyl etherified cellulose, such as ethyl cellulose and hydroxyethyl cellulose. Another sizing agent is polyvinyl methyl ether. One type or two or more types of the above-mentioned sizing agents can be used. These sizing agents are applied as an aqueous liquid to the fiber bundle to be treated. Usually, sizing agent is 1g/~20g/
Use as an aqueous solution. As the solvent, water alone or a mixed solvent of water and acetone, methanol, ethanol, etc. is used. The use of a mixed solvent is effective when using water alone as a solvent becomes difficult to use due to high solution viscosity. When the viscosity of the solution increases, the strands (fiber bundles) tend to stick to each other, causing fluff after drying. When using a mixed solvent, the organic solvent should be 40-80%
used in aqueous solutions containing The amount of deposited sizing agent needs to be 0.01 to 0.5% by weight. If it is less than 0.01% by weight, it will not be effective in suppressing fuzz, and if it exceeds 0.5% by weight, it will cause the strands to stick together and stick together after carbonization.
The preferred range is 0.1-0.3% by weight. Usually, the aqueous sizing agent liquid is applied to the fiber bundle to be treated by any method such as passing the fiber bundle immersed in the aqueous liquid, spraying the aqueous liquid onto the fiber bundle, or bringing the aqueous liquid into contact with the fiber bundle. In order to attach the aqueous sizing agent to the flame-resistant fiber bundle, whichever of the above methods is used, it is preferable to squeeze and dry the sizing agent with a pressing roller after the adhesion. This is because the aqueous sizing agent is attached to the flame-resistant fibers, which is squeezed with a presser roller while preventing surface damage, and the agglutination that occurs during the flame-proofing process is defibrated to reduce the moisture content of the fiber bundle after squeezing.
This is because drying in a state of about 45% allows the strands to be dried without sticking to each other during drying. After applying the sizing agent, dry at a temperature below 250°C. If the fiber is introduced into the carbonization furnace without drying, the strength of the product fiber will decrease. Furthermore, if the fiber is dried at a temperature exceeding 250°C, the fiber bundles will stick together and the performance of the product fiber will deteriorate. It is preferable to apply the sizing agent and dry the strand while it is in the state of being carbonized. If the strands are doubled, skeined, or wound around a skein or bobbin, the strands will adhere to each other, which is inconvenient. Tables 1 and 2 below show the influence of the amount of sizing agent deposited and drying temperature on flame-resistant fibers.

【table】

[Fuzz count measurement method]

After soaking the 6000 filament strand in acetone to dissolve and remove the sizing agent, approximately 1.5 m
The fibers were stretched to a length of 100 mm, air-dried with acetone, opened with air, and the number of protruding fuzz was counted over a length of 1 m. [Method for measuring stickiness number] Cut 6000 filament strands into 3mm lengths, put them into acetone, perform ultrasonic cleaning to dissolve and remove the sizing agent, and then measure using a microscope.
Count the thick glue threads under 6.3 magnification.

【table】

Claims (1)

[Claims] 1. When supplying a flame-resistant fiber bundle to a carbonization furnace and continuously heat-treating it to produce acrylonitrile-based carbon fiber, the flame-resistant fiber bundle is preliminarily treated with polyethylene oxide having a molecular weight of 100,000 or more, ethyl etherification, or hydroxyethyl etherification. cellulose,
Or (and) depositing an aqueous solution of polyvinyl methyl ether, with a deposit amount of 0.01 to 0.5% by weight.
A method for producing carbon fibers, which comprises drying the fibers, followed by drying at a temperature of 250° C. or lower, and then carrying out the heat treatment.